Drive mechanism for magnetic recorders



Nov. I7, 1953 M. CAMRAS 2,659,541

DRIVE MECHANISM FOR MAGNETIC RECORDERS Filed Dec. 31, 1946 3Sheets-Sheet 1 IN VEN TOR.

MAR vw CA MR/l s.

Nov. 17, 1953 M, c M s 2,659,541

DRIVE MECHANISM FOR MAGNETIC RECORDERS Filed Dec. 31, 1946 3Sheets-Sheet 2 Q JNVENTOR.

MARI/IN CAMQA s Nov. 17, 1953 M. cAMRAs 2,65

DRIVE MECHANISM FOR MAGNETIC RECORDERS I l g 4;757. e

INVENTOR.

Patented Nov. 17, 1953 UNITED STATES PATENT OFFICE DRIVE. MECHANISM FORMAGNETIC 'RECORDERS nois ApplicatiolfDecember 31, 1946,Ser-ial-No;719,=883

A Claims. (01. 242-54) This invention relates to a magnetic recorder,and more particularly: to; thev drive mechanism of a magnetic'recorder.

In magnetic recorders, anelongated magnetic record member is moved overan electromagnetic transducer headiatisubstantially a uniform rate ofspeed. It is important in;all magnetic recorders to provideanl'efficient yet simple method of handlingthe elongated-record-member,and to this end,, mostamagnetic recorders include a supply spool fromwhich thewrecord mcmber is unwound and .a taker-up spool on which therecord member isu-wound up. The electroma netic transducerhead;is;interposed between the two spools and the record memberiscausedto pass thereover :or therethrough.

Magnetic recordersmay be generally. classified as spool-drive recordersor, as capstan-drive recorders. These two .termsare used rather broadlyto referito drive mechanisms in which the take-up spool is driven at aconstantan ular velocity and inywhichan intermediate drive mechanism isprovided for causing the record member to-travel at a uniform linearvelocity across the transducer head, respectively.

While it is well recognized that-capstandrives are more satisfactoryfrom the standpoint of 7 quality of recording and reproduction; they.have nevertheless not been used as :widely as. have spool drives becauseof the usuallyconsidered greater complexityof a capstan drivetype .ofsystem.

One of the principal features and objects of the present invention is toprovide a-novel drive mechanism for a magnetic recorder of: the capestan type.

It should be pointed-out that astheexpression magnetic recorder is usedthroughout, it refers to a device whicheither magnetically records ormagneticallyreproduces or does both.

acteristic of: my invention: are set V forth with;

'40 A further object ,ofrthe present invention is r tionr toe theovithiurth ct e vantages thereof may best be understood by referencetotheiollowing description talg'en in connection with the accompanyingdrawings, in which:

Figure 1, is a plan viewofarnagneticrecorder embodyin th novelteach 9the pre n -i vention;

Fi ures is a ver icahs c iqn V as taken along the lme II- lI oi.lf-igure 1;

Fi ur 3 is a raementar View. o t i te mediate drive rolls as viewedalong the line III- -III of Figure 2;

Figure 4 is a fragmentary vertical sectional view throughthetakemp-spool and its associated spind-1e;mount ing mechanism as takenalong thelineIV-eIVpf Figure 1;

Figurev 5 is an-exploded viewpf the take-up spool drive mechanism-whichis shown in assembled position in; Figure 4; and

Figure 6 is a fragmentary vertical sectional view of the brake andspindle of thesupply spool as taken-along the-linel/fL-NI ofFigure 1.

As showni F ure pft r wi s, t e netic recorder includes a case orhousing. [chaving; a top paneli I I ;upon.which a supply spool I2 and atake up rspool {3 are arranged'to be mounted on spindles l4 and I5,respectively. Also mounted on the panel II is an electromagnetictransducer headi6 adjacent a capstan roller- H, the latter-beingarranged to be driven at a uniform angulanvelgcityin a manner presentlyto be described; in order toimpart uniform linear velocity to. theelongated recordmember I8 which .is. bei woun ite t e. su l s oo l2 andwoundup;on -the take upspool l3.

Also located on thepanel illis a volumecontrol knob l9;;inc luding;anon-off switch for the audio amplifien-a toggle switchiil forturning themotor errand; ofl and, a microphoneandfhigh frequency jack -2 l "I -'hepower supply om Z2 is also arranged to; enter; the unit through, the toppanel. i l,-so that;the,entire device may be: re-

- Figures 2 to 6;of the-drawings.

- In Figure: 1, 'the ge neral outer appearance of the illustratedembodiment of the presentinventionhas been shown.

Iurning nowto figure}, itwill be seen that and a. great part of theoperating mechanism of the device is mounted below the panel II. Forpurposes of simplicity of illustration, the loud speaker has beenremoved in order not to conceal the amplifier and part of the drivemechanism, but it is to be understood that it is mounted in the front ofthe housing II] to the right of the motor and in front of the amplifiertubes 23. The audio amplifier has not been illustrated in detail, sinceany forrfi of audio amplifier may be employed but it will be understoodthat the audio amplifier is represented diagrammatically by the tubes 23as mounted on the sub-chassis 24.

On the left side of the housing I8 is located a motor 25 which isarranged to drive the takeup spindle I5 and the capstan I1. The motor 25is supported from a suitable bracket 26. The motor 25 has a double-endedarmature shaft 21 which projects both above and below the housing 28 ofthe motor 25. A fan 29 is mounted on the lower end of the armature shaft21 and suitable apertures 38 are provided in the bottom wall of thecasing ID for permitting air to be drawn in through the casing andcirculated throughout the interior of the housing.

The upper end of the armature shaft is provided with a drive pulley 3Iwhich is connected through a flexible endless belt 32 to a relativelylarge pulley 33 mounted on the spindle I5. This causes rotation of thespool I3 in a clockwise direction as viewed in Figure 1 when the motoris driven in a clockwise direction (the assumed direction of rotation ofthe motor in the illustrated embodiment of the invention).

The armature shaft 21 projects upwardly beyond the drive pulley 3| andin this upper region is engaged by a rubber tired intermediate driveroller 34, the latter being in turn engaged by the metal drive wheel 35which is mounted on the capstan drive shaft 36 carrying the capstan I1.

The drive wheel 35 is preferably given sufficient mass so that inaddition to acting as a drive roller, it also acts as a fiy-wheel tostabilize the rotary motion of the capstan when the machine is inoperation.

The intermediate rubber tired drive roller 34 is mounted on the upperbracket portion 31.

The ratio relationship of the size of the drive pulley 3| to the largepulley 33 is such that the take-up spool or reel I3 always tries todrive the record member I8 faster than the capstan I1 even for the firstlayer of the record member on the drum 38 of the take-up spool (seeFigures 4 The drive mechanism is so arranged, however, that there is noslippage between the record member I8 and the capstan I1, but theslipping clutch is provided for the drive to the spool I3, and aslipping brake is provided for the spool I2 as will now be described.

Referring now to Figures 4 and 5 of the drawings, the spindle I5, uponwhich the large drive pulley 33 is mounted at the lower end, projects upthrough a sleeve bearing 39 which is carried in a bearing housing 46mounted on the panel II. Spacer rings M and 42, spaced apart by a smallwasher 43, separate the drive pulley 33 from the bearing housing 48 andthe bearing 39.

A clutch plate 44 carrying a brake ring 45 is secured to the spindle I5in any suitable manner, such as by means of a press fit. The uppersurface of the clutch member 44 is provided with a marginal shoulderportion 46 in which the brake ring 45 is seated. A second clutch member46 having a lock pin 41 for the spool I3 is provided with a hubportion-48 and an inner sleeve 49 which is arranged to slip over theupper end of the spindle I5 and be retained in place by means of a bolt50 which is arranged to be threaded into the upper end of the spindleI5.

In assembled position, the various elements of this drive mechanismappear as shown in Figure 4 of the drawings. The spool or reel I 3 isarranged to drop down and be supported on the upper clutch member 46.This spool or reel I3 has a central portion 5I which is provided withopenings 52 therein. One of these openings is arranged to engage andreceive the lock pin 41 on the clutch member 46, so as to preventrelative rotation between the upper clutch member 46 and the spool I3.

The weight of the spool I3 causes sufiicient biasing pressure to beexerted against the brake ring 45 carried on the lower clutch member 44'so that a driving connection is made therebetween. It will be notedthat as the weight of the spool increases due to the winding up of arecord member I8 thereon, the friction between the upper and lowerclutch members increases. This is desirable, however, as will beapparent to those skilled in the art in order to maintain substantiallyuniform tension on the record member I8 over the capstan I1,

This operational feature of the present invention will presently bediscussed in greater detail in connection with the description of theoperation of this device.

It is also desirable to provide a braking action on the supply spool I2in order to hold the record member I8 tight on the recording andreproducing head I6 and in good driving engagement with the capstan I1.The illustrated embodiment of the present invention, as is shown inFigure 6 of the drawings, includes a lower brake member 53 which issupported on the panel II and on a hub 54 which extends through thepanel II.

A brake ring 55 of any suitable braking material is also provided. Theupper brake member 56 is similar to the upper clutch member 46 of thetake-up spool drive mechanism, and includes a hub portion 51 having asleeve 58 therein through which the stub shaft I4 extends. The upper endof the stub shaft or spindle I4 is provided with a bolt 59 to removablysecure the upper brake member 56 in place. The supply spool I2 issupported on the upper brake member 56, and in order to prevent relativerotation between the supply spool I2 and this upper brake member 56, alock pin 60 is provided similar to the lock pin 41 of the take-up spooldrive mechanism.

It will be understood from the above description that the lower brakemember 53 remains stationary and is secured to the panel II, while theupper brake member 56 rotates with the supply spool I2 and is partialybraked in its rotative movement by the frictional drag between the upperbrake member 56 and the brake ring 55 carried on the lower brake member53. It will also be observed from the above description that there is anautomatically varying torque on the supply reel, for the braking torquedecreases due to the decreasing weight of the supply spool as the recordmember is unwound.

It willfurther be observed when full consideration is given to theproblem that as the take-up spool fills up it becomes heavier, and itstorque increases, but the tension (i. e., the pulling force) remainsapproximately the same. This also applies to the supply spool. If thetensioning force produced 5011 the record member .18 bythe takeup spool13, issubstantially equal to the tensioning force put on th recordmember l8 by the supplyspool I2, substantially no, driving force isrequired at h cap tan and. b n t i be no tendency to slip even thoughthe co-eiiicient, of ,;friction between the capstan and the recordmember 18 is low.

It will furthermore-be appreciated that if the tensioning force placedon the record member It by the supply spool 12 and the take -up spool 13,arefe'qual, but high, there will be more friction against the capstan.If there never 'was'to be an unbalance between the two 'tensioningforces, therewould be no necessity to have high tensionirig'force's.However, if there is an unbalance tween these two tensio'ii'iiig''forces, it is de- "s ableto havea higher tensioning force placed on therecord member 18 by the two spools, so that there will be no slippage atthe capstan. The amount of tension which is desirable is governed by themaximum unbalance likely to occur and also by the co-efiicient offriction between the capstan i'! and the record member i8.

One of the greatest advantages of the present invention is that if thedrive reel stops or slows down, the tape does not pile up for thecapstan just slips. This is a distinct advantage over using a capstanwith a drive roller positively driving the record member.

In operating the magnetic recorder of the present invention, the volumecontrol, on-oii amplifier switch [9, is turned on, and the motor switch20 is also thrown. This causes energization of the motor which rotatesthe take-up spool 13 in a clockwise direction through the belt drive 32.Energization of the motor 25 also causes rotation of the capstan It in aclockwise direction. As the record member i8, which in this instance hasbeen illustrated as a magnetic tape, is wound up on the take-up spooll3, it is unwound from the supply spool l2. Due to the fact that thebelt drive 32 tends to drive the take-up l3 faster than the speedtransmitted to the tape I8 from the capstan [7, there is a slightslippage between the clutch members 44 and 46. There is also a slippagebetween the brake members 53 and 56 and for that reason, the recordmember I8 is tensioned across the capstan H and over the electromagnetictransducer head I6.

After the record member l8 has been completely unwound from the supplyspool 12 and wound up on the take-up spool I3, the two spools areinterchanged and the spool I3 which was the take-up spool is now mountedon the supply spool spindle Id.

The head It is so constructed that its operative portion engages half ofthe width of the record member is only. It will thus be understood thatthe first time the record member I8 is moved across the head [6, half ofthe record is played back.

After the two spools are interchanged and turned upside down, the otherhalf of the record member I8 is in operative engagement with theelectromagnetic transducer head It. In this second operation, the spooll2 which was originally the supply spool, now becomes the take-up spool,and the spool l3 which was originally the take-up spool is now thesupply spool. After the record has been played back so as to reproducethe other half of the width of the record, the record is in its originalcondition. It will thus be apparent that no rewinding is necessary withthis arrangement.

abs-gar While I Havesiibwn'a articularmbodiiiielit of my invention, 'it'wilLb'f curs be understood that I do" not wish to be limited "thereto,"since many modifications may be made, and I, therefore, contemplate by't lie appendedbla'ims to cover all such modifications as .fallwithinthe trues'pirit and sc'ope' of "my" invention.

I claifn as my invention: 7 '1. A magnet c recorder comprisin an idlersupply spoolfa'iid a up*s'pool,"anelongated record memberfon semen- 5pmsp o'oland extending to said take u'pspo'ol, a'slipping friction clutch,"for drivin said," take-up spool through said frictionclutch, 'anannular friction brake member coaiiialwith "said suppiy'spoo'l forbrakin said supply's ool at a varying braking torque, drive rollerfoverand partially around which said record member extends, m :for drivingsaid 'dri've' ro'ller' at substa c611- s't'a'nt speed,'means fordrivingsaidtake-up spool through said friction clutch at a' speed tending totake up said record member at a faster speed than said drive rollerimparts to said record member, said brake being proportioned withrespect to said friction clutch to produce a tensioning force on saidrecord member substantially equal and opposite to the tension forceproduced by said drive means through said slipping friction clutch,whereby said drive roller alone determines the speed of travel of saidrecord member.

2. A magnetic recorder comprising an idler supply spool and a take-upspool, an elongated record member on said supply spool and extending tosaid take-up spool, a slipping friction clutch, means for driving saidtake-up spool through said friction clutch, an annular friction brakecoaxial with said supply spool for braking. said supply spool at avarying braking torque, a drive roller over and partially around whichsaid record member extends, said drive roller having a relatively highco-eficient of friction with respect to said record member, means fordriving said drive roller at substantially constant speed, means fordriving said take-up spool through said friction clutch at a speedtending to take up said record member at a faster speed than said driveroller imparts to said record member, said brake being proportioned withrespect to said friction clutch to produce a tensioning force on saidrecord member substantially equal and opposite to the tension forceproduced by said drive means through said slipping friction clutch,whereby said drive roller alone determines the speed of travel of saidrecord member.

3. A magnetic recorder comprising an idler supply reel and a take-upreel, an elongated record member on said supp-1y reel and extending toand arranged to be wound up on said take-up reel, a slipping frictionclutch, means for driving said take-up reel through said frictionclutch, automatically varying torque brake means 00-- axial with saidsupply reel for braking said supply reel, said brake means beingproportioned with respect to said friction clutch to produce atensioning force on said record member substantially equal and oppositeto the tension force produced by said drive means through said frictionclutch, a drive roller over and partially around which said recordmember extends, means for driving said drive roller at substantiallyconstant speed, means for driving said take-up reel through saidfriction clutch at a speed tending to take up said record member at afaster speed than said driver roller imparts aesaugi 7 to said recordmember, the torque of said brake means being automatically reduced asthe takeoflf point approaches the center of rotation of said supply reelthereby to maintain a substantially constant tensioning force on saidrecord member.

4. A magnetic recorder capstan drive mechanism for an elongated recordmedium, comprising a gravity actuated slipping clutch including atake-up spool supporting member and a subjacent driving member, agravity actuated slipping brake including a supply spool supportingmember and a subjacent stationary braking member, said brake and saidclutch having substantially equal slippage resisting characteristics foruniformly tensioning the record medium, a single capstan offset fromsaid clutch and said brake to receive the record member partiallytherearound and having a smooth driving surface over which the recordmedium may slip, and ratio drive means in driving connection with saidclutch driving member and said capstan to produce slippage of saidclutch while the record medium is taken up from said capstan, thereby totension said record member substantially equally and oppositely acrossthe smooth driving surface of said capstan during operation of themechanism.

MARVIN CAL/IRAS.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,240,560 Gilmore Sept. 18, 1917 1,398,680 Clayton Nov. 29,1921 1,640,760 Emery Aug. 30, 1927 1,789,607 Steurer Jan. 20, 19311,798,904 Schneider Mar. 31, 1931 2,179,334 Keyes Nov. 7, 1939 2,215,468Herzig Sept. 24, 1940 2,372,810 Camras Apr. 3, 1945

